If ever you were surprised by the statement of the need of a random number for signature in my post PS3 jailbroken or if you’re interested in the mathematics behind the exploit, I would recommend that you read Nate Lawson’s post DSA requirements for random k value.

Funnily, he posted that before the hack of PS3 was public. In general, his blog root lab rdist is excellent (although very technical). Nate was a former employee of CRI (the company of Paul Kocher)